JP2719393B2 - Video intermediate frequency signal processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for processing a video intermediate frequency signal, and more particularly to a video intermediate frequency signal processing device capable of coping with different broadcasting systems.

[Conventional technology]

In Europe, the Middle East, and the like, there are regions where television broadcasts from neighboring countries can be received. For such regions, television sets that can support a plurality of broadcast systems have been manufactured. Figure 6 shows SECAM (s) in France.
quenticel couleur a mmoire color TV system) L
Broadcasting signals of two broadcasting systems, one of which is AM-modulated and the audio signal is transmitted, and the other is PAL (Phase Alternation by Line) B / G system (the audio signal is FM-modulated and transmitted) FIG. 18 is a block diagram illustrating a circuit configuration of a conventional video intermediate frequency signal processing device built in a television set that can receive. The broadcast signal received by the antenna 1 is converted by the tuner 2 into a video carrier frequency f _P1 and audio carrier frequencies f _S1 and f ′ _S1 or a video carrier frequency f _P2 and an audio carrier frequency f _S2 according to the type of the broadcast signal. The video intermediate frequency signal is converted to an image SAW (acoustic surface waves) filter 3.
And the audio SAW filter 4. The video SAW filter 3 has a well-known band-pass characteristic necessary for demodulating a video intermediate frequency signal into a normal video signal, and the band-pass characteristic is as shown in FIG. Video
The video intermediate frequency signal filtered by the SAW filter 3 is supplied to a video intermediate frequency (IF) signal processing IC 5. A video IF signal processing IC (hereinafter abbreviated as VIF IC) 5 is an amplifier (hereinafter abbreviated as AMP) 6 and a video intermediate frequency LLD (Low Level Detector).
(Hereinafter abbreviated as VIF LLD) 7 and VIF LLD7 has VIF
LLD coil 7a is connected.

The audio SAW filter 4 has a band-pass characteristic A such that the frequencies f _S1 , f ′ _S1 and f _P2 are filtered, and a band-pass characteristic B such that the frequencies f _P1 and f _S2 are filtered (see FIG. 8). ). voice
The video intermediate frequency signal that has passed through the SAW filter 4 is supplied to picture trap circuits 8, 9 and a switch SW1. The picture trap circuits 8 and 9 are for removing components of the frequencies f _P1 and f _P2 , respectively. The switch SW1 is driven by a signal from the switch switching terminal 10 so that
Alternatively, the output of the audio SAW filter 4 is selectively transmitted. An audio intermediate frequency signal processing IC is provided on the output side of the switch SW1.
(Hereinafter abbreviated as QIF IC) 11 is connected. QIF IC11
Is composed of an AMP 12, an audio intermediate frequency LLD (hereinafter abbreviated as QIF LLD) 13, and a QIF LLD coil 13a is connected to the QIF LLD 13. The resonance frequencies of the VIF LLD coil 7a and the QIF LLD coil 13a change according to the signal from the switch switching terminal 10.

First, a case where a broadcast signal of the PAL B / G system is received will be described. At this time, the switch SW1 is switched to X by the signal from the switch switching terminal 10, and the VIF LLD
The resonance frequency of coil 7a and QIF LLD coil 13a is
Set to _P1 . The PAL B / G broadcast signal received by the antenna 1 is transmitted by the tuner 2 to the video carrier frequency f _P1.
And a video intermediate frequency signal having an audio carrier frequency f _S1 and supplied to the video SAW filter 3 and the audio filter 4. The video intermediate frequency signal is filtered by the band pass characteristics of these filters, and the filtered output is VIF IC5, Q
Provided to IF IC11.

The filtered output of the video SAW filter 3 is amplified by the AMP 6 and detected by the VIF LLD 7, that is, the VIF LLD coil 7.
A frequency component equal to the resonance frequency f _P1 of a is removed and demodulated into a video signal. On the other hand, the filtered output from the audio SAW filter 4 is amplified by the AMP 12 and then amplified by the QIF LLD 13
LIF coil 13
The difference between the resonance frequency f _{P1 of a} and the voice carrier frequency f _S1 is obtained, and a 5.5 MHz PAL intercarrier is output. PAL
The intercarrier is then subjected to voice detection and demodulated into a PAL voice signal.

Next, a case where a broadcast signal is received in the SECAM L system will be described. VHF High channel and UHF,
The explanation is made separately for the VHF Low channel. In the former case, the switch SW1 is switched to Y by the signal from the switch switching terminal 10, and the resonance frequencies of the VIF LLD coil 7a and the QIF LLD coil 13a are set to the frequencies f _P1 and f ′ _S1 , respectively.
The SECAM L broadcast signal is converted by the tuner 2 into a video intermediate frequency signal having the above-mentioned frequencies f _P1 and f ′ _S1 , and is supplied to the video SAW filter 3 and the audio SAW filter 4. The filtered output of the video SAW filter 3 is demodulated into a video signal by the same operation as described above. Meanwhile, audio SAW
The filtered output of the filter 4 is passed through the picture trap circuit 8 to the QIF IC11 because the switch SW1 is switched to Y.
Given to. The picture trap circuit 8 has a voice SAW
Since the component of the frequency f _P1 is removed from the filtered output of the filter 4, only the signal (audio signal) having the frequency f ′ _S1 is input to the QIF C11. This signal is amplified by AMP12 and Q
IF LLD13. Generally, since the audio modulation method in the SECAM L method is AM modulation, QIF LLD13
AM detection and demodulation into SECAM audio signal.

In the latter case, that is, in the case of the VHF Low channel, the switch SW1 is switched to Z by the signal from the switch switching terminal 10, and the VIF LLD coil 7a and the QIF LLD coil 1
The resonance frequency of 3a is set to frequencies f _P2 and f _S2 , respectively. Changing the resonance frequency of the coils 7a and 11a in this manner is based on VHF
For the low channel, the video carrier frequency changes from f _P1 to f
_This is because the voice carrier frequency changes from f ′ _S1 to f _S2 at _P2 . The magnitude relationship between the frequencies f _P2 and f _S2 is shown in FIG.
As shown in FIG. 8, the operation is reversed from the case of the VHF High channel or UHF in the PAL B / G system or the SECAM L system. The VHF Low channel broadcast signal is converted by the tuner 2 into a video intermediate frequency signal having the above-mentioned frequencies f _P2 and f _S2 , and supplied to the video SAW filter 3 and the audio SAW filter 4. The filtered output of the video SAW filter 3 is demodulated into a video signal by the same operation as described above. Meanwhile, voice SA
The filtered output of the W filter 4 passes through the picture trap circuit 9 to the QIF IC1
Given to one. The picture trap circuit 9 is an audio SAW
Since the component of the frequency f _P2 is removed from the filtered output of the filter 4, only the signal (voice signal) having the frequency f _S2 is input to the QIF IC 11. Then, similarly to the case of the VIF High channel, AM detection is performed by the QIF LLD 13 and demodulated into a SECAM audio signal.

[Problems to be solved by the invention]

The conventional video intermediate frequency signal processing device is configured as described above, and includes two picture trap circuits 8, 9, components and switches for changing the resonance frequency of the coils 7a, 13a.
The necessity of the SW1 increases the number of components, complicates the configuration of the peripheral circuit of the QIF IC11, and increases the cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain a video intermediate frequency signal processing device having a small number of components.

[Means for solving the problem]

A video intermediate frequency processing device according to the present invention includes: input means for inputting a video intermediate frequency signal having a video signal component of a video carrier frequency and an audio signal component of an audio carrier frequency determined for each broadcast system; and A video filter, connected to the video intermediate frequency signal, for outputting the first filtered output by passing the video signal component from the video intermediate frequency signal, and including a voltage-controlled oscillator, having the video carrier frequency connected to the video filter. A phase-locked loop circuit that outputs a lock signal that is phase-locked to the first filtered output from the voltage controlled oscillator, and is connected to the video filter and the phase-locked loop circuit, and outputs the first filtered output to the lock signal. A video detector that detects and outputs the video signal by using a band centered on the audio carrier frequency of each of the broadcasting systems. An audio filter group that has a plurality of audio filters having pass characteristics and is connected to the input means, filters the video intermediate frequency signal, and outputs a plurality of second filtered outputs; and Switching means for selectively transmitting one of the plurality of second filtered outputs of the audio filter group, according to the broadcast system based on the video intermediate frequency signal, the voltage controlled oscillator, and A multiplier connected to switching means for multiplying the lock signal and the second filtered output provided via the switching means to output a first audio signal; and An oscillator for generating a signal synchronized with a signal component, connected to the switching means, and providing the second filtered output provided through the switching means to the It detects by using the output signal of the oscillator, and a speech detector for outputting a second audio signal.

[Action]

In the present invention, the phase locked loop circuit including the voltage controlled oscillator provided on the video signal processing side outputs a lock signal having a video carrier frequency and being phase locked to the first filtered output from the voltage controlled oscillator. Then, this is given to a multiplier provided on the audio signal processing side. The audio filter group filters the video intermediate frequency signal with bandpass characteristics centered on different audio carrier frequencies, and outputs a plurality of second filtered outputs. The switching means is switched in accordance with the broadcasting system based on the video intermediate frequency signal, and selectively outputs any one of the plurality of second filtered outputs. The multiplier is provided with one of a plurality of second filtered outputs via switching means. The multiplier performs a multiplication process of the lock signal from the video signal processing side and the second filtered output, and outputs a first audio signal, for example, a PAL intercarrier. An audio detector detects the second filtered output provided via the switching means using a signal having the audio carrier frequency and synchronized with an audio signal component, and outputs a second audio signal, for example, a SECAM audio. Output a signal.

〔Example〕

FIG. 1 is a block diagram showing a configuration example of a video intermediate frequency signal processing device according to the present invention. The broadcast signal received by the antenna 1 is converted into a video carrier frequency f _P1 and audio carrier frequencies f _S1 and f ′ _S1 or a video carrier frequency f _P2 and an audio carrier frequency f _P1 according to the type of the broadcast signal in the tuner 2 as in the related art. _The signal is converted into a video intermediate frequency signal having _S2, and supplied to the video SAW filter 3 and the audio SAW filters 4a and 4b. The video SAW filter 3 has the same band pass characteristics as the conventional one (see FIG. 7). The filtered output of the video SAW filter 3 is provided to an intermediate frequency processing IC (hereinafter abbreviated as IF IC) 20.

As shown in FIG. 2, the bandpass characteristics of the voice filter 4a are such that the voice carrier frequencies f _S1 and f ′ _S1 of the PAL B / G system and the SECAM L system are both filtered. The filtered output of the audio filter 4a is provided to the switch SW2.

The audio SAW filter 4b has a frequency f _S2 as shown in FIG.
Has a symmetric band-pass characteristic centered at the center, and its filtered output is provided to a switch SW2. The switch SW2 is switched by a signal from the switch switching terminal 10. IF IC
20 is AMP21,22, phase locked loop (hereinafter referred to as PLL)
PLL image detector including circuit 23, PLL AM including PLL circuit
It comprises a detector 24 and a multiplier 25. The AMP 21 amplifies the filtered output of the video SAW filter 3 and supplies it to the PLL video detector 23. PLL
The video detector 23 includes a voltage-controlled oscillator (hereinafter, referred to as
VCO), and the oscillation frequency of the VCO changes according to a signal from the switch switching terminal 10. The AMP 22 is connected to the switch SW2, amplifies the filtered output provided through the switch SW2, and supplies the amplified output to the PLL AM detector 24 and the multiplier 25. The PLL AM detector 24 includes a VCO as described later, and the VCO also changes its oscillation frequency in accordance with a signal from the switch switching terminal 10.

The multiplier 25 multiplies the VCO output of the PLL video detector 23 by the output of the AMP 22.

FIGS. 4 and 5 are block diagrams showing one configuration example of the PLL video detector 23 and the PLL AM detector 24, respectively. These configurations are the same as those of a PLL VIF IC that is generally commercially available. . In FIG. 4, the video intermediate frequency signal supplied from the AMP 21 is supplied to an automatic phase comparator (hereinafter abbreviated as APC) 23a and a video detector 23b. The video detector 23b detects the video intermediate frequency signal, and the detection output is amplified by the video AMP 23c and output as a video signal. On the other hand, the APC 23a compares the frequency and phase of the video intermediate frequency signal with the oscillation frequency and phase of the VCO 23d, and generates an average DC voltage proportional to the error. This error voltage is applied to the control terminal of the VCO 23d via the low-pass filter 23e, and changes the oscillation frequency of the VCO 23d in a direction to reduce the oscillation frequency difference and the phase difference between the video intermediate frequency signal and the VCO 23d. Locked to video carrier frequency. The locked oscillation frequency (VCO output) of the VCO 23d is supplied to the multiplier 25.

The configuration of the PLL AM detector 24 shown in FIG. 5 is different from that of the PLL video detector 23 shown in FIG.
24b is equivalent to replacing video AMP23c with audio AMP24c. The AM detector 24b performs AM detection on the audio intermediate frequency signal from the AMP 22, and the AM detection output is amplified by the audio AMP 24c and output as an audio signal. Other configurations and operations are the same as those of the PLL video detector 23. Note that the oscillation frequency of the VCO 24d is finally locked to the voice carrier frequency.

As described above, a method of separately inputting a video intermediate frequency signal and an audio intermediate frequency signal and processing each signal using a PLL circuit is generally called a PLL split method.

In the operation of the circuit of FIG. 1, a case where a broadcast signal of the PAL B / G system is received will be described first. At this time, the switch SW2 is set to X1 by the signal from the switch switching terminal 10.
Switch to. In response to this, the free-running oscillation frequencies of the VCOs 23d and 24d are set, and the PCO in the PLL video detector 23 and PLL AM detector 24 are set.
The LL loop locks to the video carrier frequency f _P1 and the audio carrier frequency f _S1 of the PAL B / G system, respectively. The PAL B / G broadcast signal received by the antenna 1 is converted by the tuner 2 into a video intermediate frequency signal having a video carrier frequency f _P1 and an audio carrier frequency f _S1 , and the video SAW filter 3 and the audio S
It is provided to AW filters 4a and 4b. The AMP 21 amplifies the filtered output of the video SAW filter 3 and supplies the amplified output to the PLL video detector 23.
The video detector 23 demodulates the filtered output into a video signal using the oscillation output of the VCO 23d.

Since switch SW2 is switched to X1, audio SAW
The filtered output of filter 4a is provided to AMP22 and amplified,
This is provided to the multiplier 25. The multiplier 25 is a PLL video detector 23
And the output of AMP22 are multiplied to obtain the frequencies f _P1 and f
Outputs the difference from _S1 (5.5 MHz), that is, PAL intercarrier.

Next, a case where a broadcast signal of the SECAM L system is received will be described. The case of the VHF High channel and UHF and the case of the VHF Low channel will be described separately. In the former case, switch SW2 is set to X1 as in the PAL B / G system.
Switch to. In response, the free-running oscillation frequencies of the VCOs 23d and 24d are set, and the PLL video detector 23 and the PLL AM detector 24
Are locked to the video carrier frequency f _P1 and the audio carrier frequency f ′ _S1 of the SECAM L system VHF High channel, respectively. The broadcast signal received by antenna 1 is PAL
As in the case of the B / G system, the tuner 2 converts the signal into a video intermediate frequency signal having a video carrier frequency f _P1 and an audio carrier frequency f ′ _S1 , and supplies the same to the video SAW filter 3 and the audio SAW filters 4a and 4b. Then, the video intermediate frequency signal is demodulated into a video signal by the same operation as in the case of the PAL G / B system. The filtered output of the audio SAW filter 4a is supplied to the AMP 22 via the switch SW2. Since the sound modulation method of the SECAM L method is generally AM modulation, the PLL AM detector 24
The output of AMP22 is demodulated into a SECAM audio signal using the oscillation output of d.

In the latter case, that is, in the case of the VHF Low channel, the switch SW2 is switched to Y1 by a signal from the switch switching terminal 10. In response to this, the free oscillation frequencies of the VCOs 23d and 24d are set, and the PLL loops in the PLL video detector 23 and the PLL AM detector 24 are the video carrier frequency f _P2 and the audio carrier frequency f of the SECAM L system VHF Low channel, respectively. Lock to _S2 . The broadcast signal received by the antenna 1 is converted by the tuner 2 into a video intermediate frequency signal having frequencies f _P2 and f _S2 , and the video SAW filter 3 and the audio SAW filters 4a and 4b
Given to. Then, the video intermediate frequency signal is demodulated by the PLL video detector 23 into a video signal by the same operation as described above. Since the switch SW2 is switched to Y1, filtered output filters the video intermediate frequency signal in the audio SAW filter 4b of the band-pass characteristic centered on the frequency f _S2 is given to AMP 22, AMP 22 is amplified and the filtrate wave output And give it to the PLL AM detector 24. The PLL AM detector 24 detects the output of the AMP 22 using the oscillation output of the VCO 24d, and outputs a SECAM audio signal.

According to the above embodiment, audio signals of the audio carrier frequencies f _S1 (f _S1 ′) and f _S2 are individually extracted by the audio SAW filters 4a and 4b, and in the case of the PAL B / G system, Since the PAL intercarrier is obtained by using the output of the VCO 23d in the PLL video detector 23 locked to the phase and frequency of the video carrier frequency f _P1 component of
It is not necessary to use a picture trap circuit conventionally used, and the number of components is reduced. Therefore, the circuit configuration is simplified, and cost reduction can be achieved. Further, since the PLL split system is used, voice sensitivity and buzz characteristics are improved.

In the above embodiment, the case where the broadcast signals of two broadcast systems are received has been described. However, the present invention can be applied to the case of receiving the broadcast signals of three or more broadcast systems.

〔The invention's effect〕

As described above, according to the present invention, a lock signal including a voltage controlled oscillator, connected to a video filter, having a video carrier frequency and being phase locked to the first filtered output is output from the voltage controlled oscillator. A phase locked loop circuit, a video filter connected to the video filter and the phase locked loop circuit, and a video detector for detecting a first filtered output from the video filter using a lock signal and outputting a video signal; A plurality of audio filters having band-pass characteristics centered on, connected to the input means, an audio filter group for filtering the video intermediate frequency signal and outputting a second filtered output, and connected to the video filter group. Switching means for selectively transmitting one of a plurality of second filtered outputs of an audio filter group in accordance with the broadcasting system based on the video intermediate frequency signal , It is connected to the voltage controlled oscillator and switching means, first performs a multiplication of the second filter output provided via a phase lock signal and the switching means
A multiplier that outputs an audio signal and an oscillator that has an audio carrier frequency and generates a signal synchronized with the audio signal component,
An audio detector that is connected to the switching means, detects the second filtered output provided via the switching means using the output signal of the oscillator, and outputs a second audio signal, without using a picture trap circuit. For example, PAL
Since the B / G intercarrier and the SECAM L audio signal are obtained, the circuit configuration is simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a video intermediate frequency signal processing device according to the present invention, FIGS. 2 and 3 are diagrams showing band pass characteristics of an audio SAW filter applied to the present invention, FIG. 4 is a block diagram showing a configuration example of a PLL video detector, FIG. 5 is a block diagram showing a configuration example of a PLL AM detector, and FIG. 6 shows a configuration of a conventional video intermediate frequency signal processing device. FIG. 7 is a block diagram showing the band pass characteristics of the video SAW filter included in the apparatus shown in FIG. 6, and FIG.
The figure shows the bandpass characteristics of the audio SAW filter included in the device shown in FIG. In the figure, 1 is an antenna, 2 is a tuner, 3 is an image
SAW filter, 4a and 4b are audio SAW filters, 10 is a switch switching terminal, 23 is a PLL video detector, 24 is a PLL AM detector,
25 is a multiplier and SW2 is a switch. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. An input means for inputting a video intermediate frequency signal having a video signal component of a video carrier frequency and an audio signal component of an audio carrier frequency determined for each broadcast system, and said video intermediate signal being connected to said input means. A video filter for passing the video signal component from a frequency signal to output a first filtered output; and a voltage controlled oscillator connected to the video filter and having the video carrier frequency and the first filtered output. A phase-locked loop circuit that outputs a lock signal that is phase-locked to the voltage-controlled oscillator, and is connected to the video filter and the phase-locked loop circuit, and detects the first filtered output by using the lock signal. A video detector that outputs a video signal, and a plurality of band-pass characteristics centered on the audio carrier frequency of each of the broadcast systems. An audio filter group connected to the input means, for filtering the video intermediate frequency signal, and outputting a plurality of second filtered outputs; and an audio filter group connected to the audio filter group, Switching means for selectively transmitting one of the plurality of second filtered outputs of the audio filter group in accordance with the broadcasting system according to the following, connected to the voltage controlled oscillator and the switching means, A multiplier for multiplying the lock signal and the second filtered output provided via the switching means and outputting a first audio signal; a signal having the audio carrier frequency and synchronized with the audio signal component And an oscillator for generating the second filtered output, which is connected to the switching means and provided through the switching means, using an output signal of the oscillator. Detection, and video intermediate frequency signal processing device and a voice detector for outputting a second audio signal.